by Judith Curry
Politics versus science in attributing extreme weather events to manmade global warming.
If you follow me on twitter, you may have noticed that I was scheduled to testify before the House Oversight and Reform Committee on Jun 12 [link]. The subject of the Hearing is Contending with Natural Disasters in the Wake of Climate Change.
Late on Jun 10, I received an email telling me that the Hearing is postponed (as yet unscheduled). Apparently the Committee finds it more urgent to have a Hearing related to holding the Attorney General and Secretary of Commerce in contempt of Congress [link]. Interesting to ponder that Congressional procedural issues are deemed to be more important than Climate Change.
So I spent all last week working on my testimony (which is why there have been no new blog posts). I hope the Hearing will eventually happen (Michael Mann is also scheduled to testify).
Hurricanes and climate change constitute a major portion of my testimony. You may recall my recent series on Hurricanes & climate change [link]. Specifically with regards to detection and attribution, my bottom line conclusion was:
“In summary, the trend signal in hurricane activity has not yet had time to rise above the background variability of natural processes. Manmade climate change may have caused changes in hurricane activity that are not yet detectable due to the small magnitude of these changes compared to estimated natural variability, or due to observational limitations. But at this point, there is no convincing evidence that manmade global warming has caused a change in hurricane activity.”
I’m sure many would dismiss this conclusion as ‘denial’, in spite of the extensive documentation and logic of my arguments. Lets dig into:
- the latest from the hurricane researchers
- ‘storylines’ from non-hurricane researchers
- why blaming extreme events on AGW is important in ‘winning’ the public debate
- what happens when scientists get in the way of AGW activist ‘scare stories’ about extreme events
- ‘scaring the children’ strategies
New review paper – Knutson et al.
Earlier this week I spotted an in press review article entitled Tropical Cyclones and Climate Change Assessment: Part I. Detection and Attribution [link].
There are 10 coauthors on the paper:
“The authors of this report include some former members of the expert team for the WMO 2010 assessment (Knutson et al. 2010) along with current membership of a WMO Task Team on Tropical Cyclones and Climate Change. The Task Team members were invited to become members by the WMO World Weather Research Program’s Working Group on Tropical Meteorology Research.”
Excerpts from the Summary:
“In this assessment, we have focused on the question: Can an anthropogenic influence on TC activity be detected in past data? We explore this question from two perspectives: avoiding/reducing either Type I or Type II errors, since we presume that different audiences will have different preferences on which type of error should be avoided to a greater extent.
Using the conventional perspective of avoiding Type I error, the strongest case for a detectable change in TC activity is the observed poleward migration of the latitude of maximum intensity in the northwest Pacific basin, with eight of 11 authors rating the observed change as low-to-medium confidence for detection (with one other author having medium and two other authors having medium-to-high confidence). A slight majority of authors (six of 11) had only low confidence that anthropogenic forcing had contributed to the poleward shift. The majority of the author team also had only low confidence that any other observed TC changes represented either detectable changes or attributable anthropogenic changes.
Regarding storm surge, our expectation is that a widespread worsening of total inundation levels during storms is occurring due to the global mean sea level rise associated with anthropogenic warming, assuming all other factors equal, although we note that no TC climate change signal has been convincingly detected in sea level extremes data. To date, there is not convincing evidence of a detectable anthropogenic influence on hurricane precipitation rates, in contrast to the case for extreme precipitation in general, where some anthropogenic influence has been detected.
The relatively low confidence in TC change detection results from several factors, including: observational limitations, the smallness of the expected human-caused change (signal) relative to the expected natural variability (noise), or the lack of confident estimates of the expected signal and noise levels.”
JC comments: This paper illustrates an approach that is very unusual in the annals of climate change assessments. The sea level rise community is also using expert elicitation (e.g. Bamber et al.). Expert elicitation and and expert structured judgment is much preferred over ‘consensus seeking’. The Knutson et al. paper is distinguished by clearly explaining the evidence and and arguments that the individual scientists are considering, and in the Supplementary Information also showing individual responses.
Experts disagree on most aspects of climate change. Why do they disagree? I have covered this extensively before, the main reasons are summarized as:
- Insufficient & inadequate observational evidence
- Disagreement about the value of different classes of evidence (e.g. paleoclimate reconstructions, models)
- Disagreement about the appropriate logical framework for linking and assessing the evidence
- Assessments of areas of ambiguity & ignorance
- Belief polarization as a result of politicization of the science
The specific reasons for disagreement on a given issue need to be clarified, which the Knutson paper does. Distinguishing between Type I and II errors is also useful, which clearly identifies the speculative issues as scientifically informed speculation.
ATTP has a joint blog post with philosopher Eric Winsberg entitled Extreme weather event attribution.
Eric has just published, together with Naomi Oreskes and Elisabeth Lloyd, a paper called Severe Weather Event Attribution: Why values won’t go away. The paper discusses the issue of how one might assess the anthropogenic influence on an extreme weather event. This post describes what was presented in the paper and tries to justify why there may be value in approaching this issue from more than one perspective.
A complementary approach is to consider a storyline. For example, given that an event has occured, how might climate change have influenced this event? If the air was warmer, then we may expect enhanced precipitation. If sea surface temperatures are high, then we may expect a tropical cyclone to be more intense. The focus here tends to be on the thermodynamics (i.e., the energy) and to take the dynamics as given (i.e., the event happened).
It turns out, though, that the story-line approach has been rather controversial, with many who favour more formal detection and attribution being highly critical. They argue that it could lead to more false positives and that taking the dynamics as given ignores that dynamical factors could actually work to make some events less likely. Essentially, they argue that the storyline approach may over-estimate anthropogenic influences, potentially mistaking natural variability as being anthropogenic.
The problem, though, is that although the two approaches are complementary, they’re not actually quite addressing the same issue. The detection and attribution approach is essentially trying to determine how anthropogenic-driven climate change influences the probability of a specific class of event. The storyline approach, on the other hand, is more looking at how anthropogenically-driven climate change might have influenced an event that has actually occurred. There is no real reason why we should prefer one approach over the other; they can both play an important role in aiding our understanding of how anthropogenic influences impact extreme weather events.
JC comment: The epistemic status of formal detection and attribution approaches, versus the storyline approach, should be obvious to all CE readers.
The ‘storyline’ approach is useful for posing hypotheses for for further investigation (and avoiding possible Type II errors). However, these ‘storylines’ are generally posed by climate researchers rather than by meteorological experts on that particular type of extreme weather.
In any event, using such storylines, and claiming (even implicitly) that they are part of the AGW ‘consensus’ is scientifically dishonest.
Roger Pielke Jr’s story
As scientists are interviewed following each hurricane, speculative storylines about hurricanes and global warming abound in the public discourse on climate change. Some of these manage to get published. However, nearly all get knocked back by serious assessments.
As an example, recall the ‘storyline’ whereby Hurricane Sandy (wind speeds equivalent to a Cat 1 hurricane at landfall) was influenced by some magical steering effect associated with AGW that steered to the storm to New York City. Well, the recent U.S. National Climate Assessment Report tackled this one head on (Appendix C, Box C.2) and concluded:
“[T]here is low confidence in determining the net impact to date of anthropogenic climate change on the risk of Sandy-like events, though anthropogenic sea level rise, all other things equal, has increased the surge risk.”
For a more complete discussion, see my previous blog post on hurricanes and attribution to climate change.
Roger Pielke Jr. has been tireless in calling out scientists and others who make statements attributing hurricane impacts to climate change, citing the IPCC and other national/international assessments.
For this, Roger Pielke Jr has been massively attacked and ostracized. See this recent article by Ross McKitrick that appeared in the Financial Post “This scientist proved climate change isn’t causing extreme weather — so politicians attacked“:
“Roger Pielke Jr. is a scientist at University of Colorado in Boulder who, up until a few years ago, did world-leading research on climate change and extreme weather. He found convincing evidence that climate change was not leading to higher rates of weather-related damages worldwide, once you correct for increasing population and wealth. He also helped convene major academic panels to survey the evidence and communicate the near-unanimous scientific consensus on this topic to policymakers. For his efforts, Pielke was subjected to a vicious, well-funded smear campaign backed by, among others, the Obama White House and leading Democratic congressmen, culminating in his decision in 2015 to quit the field.”
If you are unfamiliar with the details of all this, they are quite chilling. RPJr has prepared a twitter thread on his talk ‘Extreme Weather and Extreme Politics” which is a must read. Incidents include:
- the coordinated effort of the Center for American Progress to get RPJr fired from his position on 538
- shenanigans (corruption, really) in the IPCC AR4 Section 126.96.36.199 that passed off an unpublished graph as being published and miscited it, so that they could claim an influence of warming on disaster losses
- Grijalval inquisition
- Dr John Holdren (President Obama’s Director of Office of Science, Technology and Policy) posted a screed on the White House web page against RPJr and his findings on disasters and climate change, which were highly inappropriate (not to mention scientifically incorrect).
Why extreme events matter in the climate debate
Why is attributing extreme events (or not) to AGW such a big deal? Well, the reason for this became apparent to me following Hurricane Katrina (2005), in the heyday of the hurricanes and global warming argument.
Lets face it, in 2005 the public found it very hard to care about 1 degree or even 4 degrees of warming — heck, the temperatures varied by that much on a day-to-day basis. If they wanted a slightly warmer or cooler climate, they could always move a few hundred miles to the north or south.
However, arguments that a relatively small amount of global warming (order 1 C) could result in more intense hurricanes, well that got their attention, particularly as the U.S. was reeling from Katrina catastrophe.
The AGW activists now had new weapon in their arsenal — attributing extreme weather events to manmade climate change. The ‘will to act’ seemed tied to alarmism about extreme weather events. Which provides a key political role for unsupported ‘storylines’ about extreme weather events.
Scaring the children
A corollary to this activist strategy is to scare school children, and enlist their help in politicizing the issue of climate change and extreme events and also convincing their parents.
The poster child for this is Swedish teenager Greta Thunberg. Several relevant articles on scaring the children over climate change:
The obvious issue is that teachers should educate children about climate science and not scare them witless about the apocalypse. The less obvious issue is the harm done by scaring children.
The other glaring example of this is the Juliana v. United States lawsuit, filed by school children (with the help of Jim Hansen and some activist organizations.) Extreme events figure prominently in what the children are worried about.
I sympathize with Greta Thunberg and the other scared children. I have my own ‘scaring children’ story to relate.
Back circa 1960, the ‘scary story’ was Russians taking over the U.S. through nuclear war or via infiltrating the U.S. This scary story was conveyed to me on a weekly basis by a nun in my Saturday Catechism class (Catholic Church). I was well and duly scared by all this. In fact I worried alot about this. When one of my parents was late to come home from shopping or an outing, I was worried that they got captured by the Russians.
In fact I worried about all this so much that I was diagnosed with a stomach ulcer at the ripe old age of 8 years old. In discussing this with my doctor (who had been apprised by my parents that I was a ‘worrier’), he told me I had nothing to worry about, and in any event there was nothing I could do about all this as a kid. And that I should enjoy my childhood. I said ‘ok’, and that was pretty much the end of my worrying about the Russians.
(Note: all this worrying was brought back into my memory by watching the TV show ‘The Americans’ which is absolutely fascinating.
Unlike Greta et al., I was told by responsible adults to stop worrying. In the case of Greta et al., they are cheered on by adults who find these children to be very useful in their propaganda efforts.
So where does all this leave us in the climate debate? There is very little in the way of extreme weather events that can convincingly be attributed to manmade global warming, even if you are assuming that all of the recent warming is manmade.
Global warming activists will continue use extreme events as an argument against fossil fuels, even though there is little to no evidence to support this. Without this argument, there is very little left to worry about in the near term regarding AGW, apart from the slow creep of sea level rise.
The shenanigans of activists and politicians in this regard are not surprising. What is horrifying is the way that schoolchildren are being used (and arguably harmed) in the interests of supporting the activists’ propaganda.
And finally, the silence of scientists who should know better, especially among those who have a vocal public presence (e.g. media interviews, twitter) is very disturbing. Although who among them would want to suffer the hassles and osctracism suffered by RPJr, myself and others.
The ‘establishment’ community of climate scientist activists has much to answer for. But insatiable media market for ‘fake news’ regarding extreme weather events assures them of a path of continued professional success for spouting alarmism regarding extreme weather events.